Seat occupancy responsive air cushion actuation and monitoring circuit

ABSTRACT

A circuit for actuating respective air cushions for the driver and passengers of a vehicle in the event of a collision includes relay contacts connected in the series network for firing the squib which controls inflation of the passenger cushion. When the seat is occupied by a passenger, a seat sensor disables the relay controlling the contact and the series network is armed. If no passenger occupies the seat the relay is energized to open circuit the series network and prevent inflation of the passenger cushion in the event of a collision. Monitoring circuitry indicates to the driver if a malfunction occurs such as the series network being armed while no passenger is present or the series network being open circuited while a passenger is present.

United states Patent [191 Gillund Oct. 23, 1973 SEAT OCCUPANCYRESPONSIVE AIR CUSHION ACTUATION AND MONITORING CIRCUIT [76] Inventor:Arden G. Gillund, 9980 S. McGraw,

Oak Creek, Wis. 53154 [22] Filed: Aug. 10, 1972 21 Appl. No.: 279,542

Primary Examiner-Kenneth H. Betts Attorney-Eugene W. Christen et al.

[57] ABSTRACT A circuit for actuating respective air cushions for thedriver and passengers of a vehicle in the event of a collision includesrelay contacts connected in the series network for firing the squibwhich controls inflation of the passenger cushion. When the seat isoccupied by a passenger, a seat sensor disables the relay controllingthe contact and the series network is armed. If no passenger occupiesthe seat the relay is energized to open circuit the series network andprevent inflation of the passenger cushion in the event of a collision.Monitoring circuitry indicates to the driver if a malfunction occurssuch as the series network being armed while no passenger is present orthe series network being open circuited while a passenger is present.

4 Claims, 1 Drawing Figure 2 lNERTIA SWITCH P l i u ii is, l 8 8PASSENGER SQUIB INERTIA SWITCH SEAT 48 SENSOP SEAT OCCUPANCY RESPONSIVEAIR CUSHION ACTUATION AND MONITORING CIRCUIT This invention relates tocircuitry for controlling inflation of cushions located within a vehiclefor protecting occupants of the vehicle in the event of a collision andmore particularly to a circuit for controlling inflation of a cushion asa function of whether the occupant to be protected by the cushion is oris not present in the vehicle.

In copending application Ser. No. 190,978, filed Oct. 20, 1971, now US.Pat. No. 3,714,627 and assigned to the assignee of the presentinvention, an actuation circuit is disclosed for initiating inflation ofa driver and passenger cushion in the event of a collision. Once thecushions have been inflated, the cushion and associated inflationapparatus must be replaced. Where the vehicle is occupied by only adriver or by a lesser number of occupants than there are cushionsinstalled in the vehicle, the inflation of all of the cushionsirrespective to the number and location of vehicle occupants isunnecessary and it would be desirable to eliminate the expense ofreplacement where inflation of the cushion was unnecessary. v

Accordingly, it is an objection of the present invention to provide acircuit for controlling inflation of a cushion located in a vehicle toarrest the forward motion of the occupant of the vehicle, which circuitis disabled when the occupant of the vehicle to be protected by thecushion is not present in the vehicle, and to provide circuitry forcontinuously monitoring for any malfunction of the circuit disablingmeans.

ln accordance with the present invention an actuation circuit isprovided for firing separate squibs for initiating inflation of driverand passenger air cushions located in the vehicle. Each of the squibs isconnected across a source of firing potential through a pair of inertiaswitches which complete the circuit for firing the squibs in response toa predetermined deceleration of the vehicle as might occur during acollision. Normally closed contacts operable by a relay coil areconnected in series with the passenger squib. The relay coil is normallyenergized from the vehicle battery through the ignition switch and atransistor switch. The transistor is rendered nonconductive by actuationof a seat sensor when a passenger occupies the vehicle to therebydisable the relay and arm the passenger squib firing circuit.Accordingly, the passenger squib firing circuit is enabled or disableddepending upon whether the passenger seat is occupied or vacant. Thecircuit further includes voltage divider means which normally produce apredetermined voltage at a monitoring junction in the actuation circuit.Second normally closed contacts operable by the relay coil are connectedbetween the monitoring junction and the vehicle battery through thetransistor so that the voltage at the monitoring junction risessubstantially if the relay coil is not energized while the passengersseat is vacant. Normally open contacts operated by the relay areprovided in parallel with the normally closed contacts in the passengersquib firing circuits so that the voltage at the monitoring junctiondrops substantially if, because of a malfunctioning of the normallyclosed contacts, the

passenger squib firing circuit is disabled while the passenger seat isoccupied. Detecting and indicating means connected with the monitoringjunction provide an indication to the vehicle driver of the substantialrise or fall in the voltage at the monitoring junction which accompaniesa malfunction in the relay.

Referring now to the single drawing, the circuit of the presentinvention controls the operation of separate air cushions located withinthe vehicle at the right front passenger and driver positions. Thecircuit comprises squibs l and 12 responsive to predetermined currentflow therethrough for respectively initiating inflation of a passengerand a driver cushion. A suitable mechanism for inflating a cushion inresponse to the current flow through the squibs 10 or 12 is described incopending application Ser. No. 142,533, filed May 12, 1971, by Noel etal., and assigned to the assignee of the present invention. One side ofeach of the squibs 10 and 12 is connected to ground through a normallyopen acceleration responsive switch 14 while the other side of thesquibs 10 and 12 are connected with a normally open accelerationresponsive switch 16 through isolating diodes l8 and 20 respectively.The switch 16 is connected with a source of direct current potentialsuch as the vehicle battery 22 through the usual ignition switch 24 anda diode 26. A suitable acceleration responsive switch is described incopending application Ser. No. 158,170, filed June 30, 1971 by Glenn A.Porter and Norman J. Roth, and assigned to the assignee of the presentinvention, A storage capacitor 28 is connected across the battery 22through a resistor 30 and the diode 26 and ignition switch 24 andprovides a secondary source of firing potential for the squibs 10 and 12in the event the battery 22 is disabled during a collision. A diode 32provides a discharge path for the capacitor 28 in parallel with theresistor 30. The diode 26 prevents discharge of the capacitor 28 throughthe net work leading to the battery 22 in the event this network isshorted during a collision.

A relay coil 34 is connected to the battery 22 through the ignitionswitch 24 and diode 26 and the emitter collectorelectrodes of NPNtransistor Q]. A biasing resistor 35 connected between the baseandcollector of the transistor Q1 biases the transistor to conductionwhen the ignition switch 24 is closed. The relay coil 34 controlsnormally closed contacts 36 connected between the squib 10 and theswitch 14. The relay 34 also operates normally closed contacts 38connected to a junction between the squib l2 and the switch 14 and tothe emitter of transistor 01 through a diode 40 and a current limitingresistor 42. The relay 34 also operates normally open contacts 44connected in series with a current limiting resistor 46 across thenormally closed contacts 36. The normally open contacts 44 and resistor46 maintain circuit continuity in the network comprising the squib 10when the contacts 36 open since in that event the contacts 44 close. Theresistor 46 is sized to prevent current flow through the squib 10 ofsufficient magnitude to fire the squib 10 if the switches 14 and 16close so that the passenger cushion is not inflated unless'the contacts36 are closed. A normally open seat occupancy responsive switch 48 isconnected between ground and the base of transistor Q1. The switch maybe a conventional pressure actuated switch which closes when the seat isoccupied or may be responsive to other indicia of seat occupancy by apassenger such as the sensor described in copending application Ser. No.228,544, filed Feb. 23, 1972 by Gillund et al., and assigned to theassignee of the present invention.

A voltage divider network comprising resistor 50 and 52 normallyestablish a predetermined voltage of approximately one-half thepotential of the battery 22 at a first monitoring junction M between thesquib 12 and the diode 20 and a second monitoring junction M between thesquib 10 and the diode 18. The monitoring junctions M and M areconnected with level detector circuitry generally designated 54 whichresponds to a substantial rise or fall in voltage level at themonitoring junctions M and M, to energize indicator means generallydesignated 56. A suitable level detector is described in copendingapplication Ser. No. 190,978, filed Oct. 20, 1971 and assigned to theassignee of the present invention. Battery voltage is applied to thedetector 54 through a filter network comprising a resistor 58 andcapacitor 60 and is regulated by a zener diode 62.

A diode 64 may, as shown by the dotted lines connection, interconnectthe squib 10 with the squib 12 through the normally closed contacts 38to provide a redundant path for actuation of the squib 10 in parallelwith the normally closed contacts 36.

The monitoring junctions M and M, will rise or drop substantially in theevent of a malfunction in the firing circuit for the squibs l and 12.For example, if the switch 16 becomes short circuited the voltagedividing resistor 50 is shunted when the voltage at the junctions M andM rise to substantially battery potential. On the other hand, if theswitch 14 becomes short circuited the voltage dividing resistor 52 isshunted and the voltage at the junctions M and M falls to approximatelyground potential. Furthermore, an open circuiting of the squibs and 12will cause the voltage at the junctions M and M respectively, to rise orfall substantially from the normal one-half battery potentialestablished by the resistors 50 and 52. The change in voltage resultingfrom any of the aforementioned malfunctions is detected by the leveldetector 54'to energize the indicator 56 and inform the driver of amalfunction.

In addition to the usual monitoring of the squib firing circuit asaforementioned, the present invention provides monitoring of the relaycoil 34 and contacts 36 and 38 for any malfunction thereof. Assumingthat the passenger seat is vacant and therefore that the seat sensor 48is open; when the ignition switch 24 is closed the transistor O1 isturned on and the relay coil 34 is energized to open the contacts 36 and38 and close the contacts 44. With the resistor 46 inserted in theseries network including the squib 10 and the switches Hand 16, currentflow through the squib 10, in the event of a collision causing theswitches 14 and 16 to close, is insufficient to fire the squib 10.Consequently, the passengers cushion will not be inflated in the eventof a collision. With the contacts 38 open, no current flows through theresistor 42 so that the monitoring junction M,, is maintained atapproximately 6 volts by the voltage dividing resistors 50 and 52. Iffor any reason the relay coil 34 is disabled while the seat sensor 48 isopen the contacts 36 and 38 will close. Upon closure of the contacts 38current flows from the transistor 01 through the resistor 42 and diode40 and the voltage at the monitoring junction M and M, rises tosubstantially the potential of the battery 22, i.e. 12 volts. This risein potential is detected by the level detector 54 and energizes theindicator 56 to inform the operator of a malfunction of the relay 34.

If on the other hand the passenger seat is occupied the base oftransistor Q1 will be grounded and will remain nonconductive when theignition switch 24 is closed thereby preventing energization of therelay coil 34. The contacts 36 and 38 will remain closed and thecontacts 44 will remain open. Accordingly, in the event of a collisioncausing the switches 14 and 16 to close, sufficient current will flowthrough the squib 10 to fire the squib 10 and initiate inflation of thepassenger cushion. if for any reason the contacts 36 do not close uponactuation of the seat sensor 48, both the contacts 44 and 36 will beopen. In that event, the voltage at the monitoring junction M drops tosubstantially ground potential and the voltage at the monitoringjunction M, rises substantially to a voltage determined by the dropacross the resistor 50 and the squib 10. Either the drop in voltage atthe junction M,, or the rise in voltage at the junction M,, issufficient to energize the indicator 62 and inform the driver of amalfunction of the contacts 36. When the diode 64 is connected and thecircuit is shown by the dotted line, the voltage at the junctions M andM, will change only if both the contacts 36 and 38 fail to close.

While only a single passenger squib has been shown, the invention isequally applicable to bilevel systems such as shown in theaforementioned copending application Ser. No. 190,978 wherein relativelyhigh and relatively low inflation rates are provided for the passengercushion depending upon the G level of the collision. Having thusdescribed my invention what i claim is: 1. In a passenger conveyanceprovided with a source of direct current potential, the combination of:

seat occupancy responsive switch means;

an inflatable cushion located in said vehicle to arrest forward motionof an occupant of the vehicle, said cushion adapted to be actuated byelectrically operated actuator means,

first and second normally open acceleration responsive switch meansconnected to opposite sides of said actuator means to form a seriesnetwork; means for connecting said series network across said source;voltage divider means adapted to be connected with said source fornormally establishing a predetermined voltage at a monitoring junctionin said series network; relay means comprising a relay coil, and firstand second normally closed contact means operable by said relay coil;means connecting said first normally closed contact means inseriesbetween said actuator means and said second accelerationresponsive switch means whereby said series network is open circuitedwhen said relay coil is energized; relay control means responsive tooperation of said seat occupancy responsive switch means forconnectingsaid relay coil to said source during seat vacancy and for disconnecting said relay coil from said source during seat occupancy; meansincluding said relay control means connecting said second normallyclosed contact means between said source and said junction whereby thevoltage at said junction changes from said predetermined voltage in theevent said relay coil is disabled during seat vacancy;

and means connected with said junction for detecting and indicating saidchange from said predetermined voltage. v

2. In a motor vehicle provided with a source of direct currentpotential; an ignition switch connected in series with said source;first and second inflatable cushions adapted to be actuated by first andsecond electrically operated actuator means, said first and secondcushions being located in said vehicle to arrest forward motion of thedriver of the vehicle and a passenger of the vehicle respectively, thecombination of:

an actuation circuit for operating said first and second actuator meansand comprising first and second normally open acceleration responsiveswitch means connected to opposite sides of said first actuator means toform a series network; means for connecting said series network acrosssaid source; relay means comprising a relay coil and first and secondnormally closed contact means operable by said relay coil, switch meansresponsive to occupancy of the vehicle by a passenger, relay controlmeans connected with said seat occupancy responsivelswitch means forcontrolling energization of saidrelay coil whereby said relay coil isenabled in response to seat vacancy and is disabled in response to seatoccupancy; means connecting said first normally closed contact means inseries with said second actuator means between said first and secondacceleration responsive switch means whereby said second actuator meansis disabled in response to seat vacancy; voltage divider means adaptedto be connected with said source for normally establishing apredetermined voltage at a monitoring junction in said series network;indicator means; means responsive to a change in voltage from said meansfurther includes normally open contact means operable by said relaycoil; a resistor connected in series with said normally open contactmeans across said first normally closed contact means whereby thevoltage at said monitoring junction changes from said predeterminedvoltage in the event said first normally closed contact means does notclose in response to disabling of said relay coil.

4. The circuit defined in claim 3 further including a diodeinterconnecting said second actuator means with said second normallyclosed contact means to provide a current path between said secondactuator means and said second acceleration responsive switch means inparallel to said first normally closed contact means and wherein saidmeans connecting said second normally closed contact means with saidsource includes a second diode poled to prevent current flow throughsaid first mentioned diode or second normally closed contact means tosaid relay coil.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 002Dated October 23, 1973 Inventor (Q s) Arden G Gi l lund It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Before the REFERENCES CITED, after "[76] Inventor: Arden G. Gillund,9980 S. McGraw, Oak Creek, Wis. 53154" insert [73] Assignee: GeneralMotors Corporation, Detroit, Mich.

Signed" and sealed this 19th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. In a passenger conveyance provided with a source of direct currentpotential, the combination of: seat occupancy responsive switch means;an inflatable cushion located in said vehicle to arrest forward motionof an occupant of the vehicle, said cushion adapted to be actuated byelectrically operated actuator means, first and second normally openacceleration responsive switch means connected to opposite sides of saidactuator means to form a series network; means for connecting saidseries network across said source; voltage divider means adapted to beconnected with said source for normally establishing a predeterminedvoltage at a monitoring junction in said series network; relay meanscomprising a relay coil, and first and second normally closed contactmeans operable by said relay coil; means connecting said first normallyclosed contact means in series between said actuator means and saidsecond acceleration responsive switch means whereby said series networkis open circuited when said relay coil is energized; relay control meansresponsive to operation of said seat occupancy responsive switch meansfor connecting said relay coil to said source during seat vacancy andfor disconnecting said relay coil from said source during seatoccupancy; means including said relay control means connecting saidsecond normally closed contact means between said source and saidjunction whereby the voltage at said junction changes from saidpredetermined voltage in the event said relay coil is disabled duringseat vacancy; and means connected with said junction for detecting andindicating said change from said predetermined voltage.
 2. In a motorvehicle provided with a source of direct current potential; an ignitionswitch connected in series with said source; first and second inflatablecushions adapted to be actuated by first and second electricallyoperated actuator means, said first and second cushions being located insaid vehicle to arrest forward motion of the driver of the vehicle and apassenger of the vehicle respectively, the combination of: an actuationcircuit for operating said first and second actuator means andcomprising first and second normally open acceleration responsIve switchmeans connected to opposite sides of said first actuator means to form aseries network; means for connecting said series network across saidsource; relay means comprising a relay coil and first and secondnormally closed contact means operable by said relay coil, switch meansresponsive to occupancy of the vehicle by a passenger, relay controlmeans connected with said seat occupancy responsive switch means forcontrolling energization of said relay coil whereby said relay coil isenabled in response to seat vacancy and is disabled in response to seatoccupancy; means connecting said first normally closed contact means inseries with said second actuator means between said first and secondacceleration responsive switch means whereby said second actuator meansis disabled in response to seat vacancy; voltage divider means adaptedto be connected with said source for normally establishing apredetermined voltage at a monitoring junction in said series network;indicator means; means responsive to a change in voltage from saidpredetermined voltage at said monitoring junction for energizing saidindicator means; means including said relay control connecting saidsecond normally closed contact means between said source and a junctionbetween said first normally closed contact means and said secondacceleration responsive switch means whereby the voltage at saidmonitoring junction changes from said predetermined voltage in the eventsaid relay coil is disabled during seat vacancy.
 3. The circuit definedin claim 2 wherein said relay means further includes normally opencontact means operable by said relay coil; a resistor connected inseries with said normally open contact means across said first normallyclosed contact means whereby the voltage at said monitoring junctionchanges from said predetermined voltage in the event said first normallyclosed contact means does not close in response to disabling of saidrelay coil.
 4. The circuit defined in claim 3 further including a diodeinterconnecting said second actuator means with said second normallyclosed contact means to provide a current path between said secondactuator means and said second acceleration responsive switch means inparallel to said first normally closed contact means and wherein saidmeans connecting said second normally closed contact means with saidsource includes a second diode poled to prevent current flow throughsaid first mentioned diode or second normally closed contact means tosaid relay coil.